Electromagnetic interference may take many forms and have widely varying impacts. Localized radiation sources may interfere with commercial aviation guidance and landing systems. Intentional jamming may cause a guided missile to go off-course, with serious consequences for non-combatants and for the missile's launchers.
The intentional jamming of guidance systems, with attendant life and death consequences, is of particular concern. A jamming source, also referred to herein as a “jammer,” may be employed to disrupt a guidance system, such as that of a missile, by overwhelming the guidance system receiver's front end. For example, in the case of a RADAR-guided missile, a jammer directs radiation of a frequency and format consistent with that employed by the missile's guidance system toward the missile in an attempt to deliver enough radiation to the guidance system's receiver to “swamp” the receiver, thereby “drowning out” the desired, guidance, signals. Because the jamming signal is not omni-directional, counter-measures that adjust the sensitivity of receivers may be employed to ameliorate the effects of such jamming. Space time adaptive processing (STAP) may be employed to determine the direction from which a jamming signal emanates. This directional information may then be employed to adjust the sensitivity of the missile's receiver, thereby forming one or more “null” sensitivity patterns. Space time adaptive processing is known and discussed, for example, in U.S. Pat. No. 6,091,361, entitled, “METHOD AND APPARATUS FOR JOINT SPACE-TIME ARRAY SIGNAL PROCESSING”, issued to Davis et al and in U.S. Pat. No. 6,252,540, entitled, “APPARATUS METHOD FOR TWO STAGE HYBRID SPACE-TIME ADAPTIVE PROCESSING IN RADAR AND COMMUNICATIONS SYSTEMS”, issued to Hale et al, which are hereby incorporated by reference. Although such anti-jamming devices are somewhat effective, locating the jamming source, rather than simply determining the direction in which it lies, would provide for a more effective solution to the problem (e.g., eliminating the radiation source in the case of a missile-guidance jammer).
A system and method that identifies the location of a radiation source would be particularly valuable, not only in thwarting guidance-system jamming, but in the location of other radiation sources.